# RevisionHistoryAdapter

interface

The revision history adapter.

The revision history adapter is an object that communicates asynchronously with the data source to fetch or save the revisions data. It is used internally by the revision history feature whenever revision data is required, a revision is created, or updated.

The adapter is optional. See the [Revision history feature integration](../features/collaboration/revision-history/revision-history-integration.md) guide to learn more.

To set the adapter, overwrite the [`RevisionHistory#adapter`](module_revision-history_revisionhistory-RevisionHistory.md#member-adapter) property.

<a id="methods">

## Methods

<a id="function-getRevision">

### `getRevision( data = { data.channelId, data.revisionId } ) → Promise<RevisionData>`

Called when the full revision data is required.

It should return a promise that resolves with the whole revision data.

#### Parameters

* `data: object`

  Properties

  * `data.channelId: string`
  * `data.revisionId: string`

#### Returns

* `Promise<RevisionData>`

<a id="function-updateRevisions">

### `updateRevisions( data, channelId ) → Promise<Array<RevisionData>>`

Called when revision(s) data is added or updated.

Multiple revisions can be added and updated at the same moment. The method is passed an array with the updated data. Each item in the array is a data object that describes a single revision. Each data object contains revision id. If the revision id does not exist in your data source (database), then a new revision should be created. Otherwise, the existing revision should be updated with passed data.

The method should return a promise that is resolved when the update is completed.

The `data` parameter only contains those properties of a revision that have changed.

Although the `data` parameter contains `createdAt` property, the revision creation date should be set by the backend of your application to ensure that all revisions will be saved with correct dates regardless of users' local system time. It is recommended to overwrite `createdAt` value whenever it is passed in the `data` parameter.

The promise may resolve with an array of objects. Each object represents an updated revision, for which `createdAt` property was set (or changed) on the backend. Each object should have `id` (string) and `createdAt` (`Date` object) properties. The returned data will be used to update revisions data in the editor with dates set on the backend.

Although the `data` parameter contains `creatorId` property, you should verify the `creatorId` value when saving a revision in the database. **However, do not overwrite the value if it was set to `null`!**

It is recommended to stringify `data.diffData` and `data.attributes` values to JSON and save them as strings in your database, and then to parse the strings when loading revisions.

#### Parameters

* `data: Array<RevisionData>`

  Array with revisions data to add or update.

* `channelId: string`

  The ID of the document for which the revisions were created.

#### Returns

* `Promise<Array<RevisionData>>`

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Full index of the CKEditor 5 API reference: [llms.txt](llms.txt)